Vibratory driving device

Abstract

A vibratory driving device ( 1 ) comprising an electromechanical transducer ( 3 ) which causes mechanical displacement according to an applied voltage, a driving shaft ( 4 ) which is held so as to be displaced in its axial direction by the electromechanical transducer and which is provided on its surface with two resistive bodies ( 8 ) extending in the axial direction and connected to the electromechanical transducer at one end, a movable member ( 5 ) which slidably engages on the driving shaft so as to contact with the two resistive bodies to connect electrically the contacted points of the resistive bodies each other, a driving circuit ( 13 ) which applies a periodical driving voltage to the electromechanical transducer, and a measuring circuit ( 15 ) which measures electric resistance between the two resistive bodies can determine a position of the movable member and has a simplified wiring ( 7 ) with low risk of disconnection.

1. A vibratory driving device comprising
 an electromechanical transducer which causes mechanical displacement according to an applied voltage, 
 a driving shaft which is held so as to be displaced in its axial direction by the electromechanical transducer and which is provided on its surface with two resistive bodies extending in the axial direction, 
 a movable member which slidably engages on the driving shaft so as to contact with the two resistive bodies to connect electrically the contacted points of the resistive bodies each other, 
 a driving circuit which applies a periodical driving voltage to the electromechanical transducer, and 
 a measuring circuit which measures electric resistance between the two resistive bodies. 
 
     
     
       2. The vibratory driving device according to  claim 1 , wherein the two resistive bodies are electrically connected to electrodes of the electromechanical transducer respectively. 
     
     
       3. The vibratory driving device according to  claim 2 , wherein the resistive bodies are made of resistive material applied beyond the drive shaft to the electromechanical transducer. 
     
     
       4. The vibratory driving device according to  claim 1 , wherein a predetermined conductive portion of the movable member contacts with the resistive body at a point. 
     
     
       5. The vibratory driving device according to  claim 1 , wherein the movable member engages with a portion of the driving shaft where the resistive body is not provided, and the movable member has a brush slidingly contacting with the resistive body. 
     
     
       6. The vibratory driving device according to  claim 1 , wherein the driving shaft is covered with an insulating material and the resistive body is formed on the insulating material. 
     
     
       7. The vibratory driving device according to  claim 1 , wherein the measuring circuit measures a current when the driving circuit applies a direct-current voltage to the electromechanical transducer. 
     
     
       8. The vibratory driving device according to  claim 1 , wherein the measuring circuit measures an average value of the current when the driving circuit applies the driving voltage to the electromechanical transducer. 
     
     
       9. The vibratory driving device according to  claim 1 , wherein the measuring circuit measures a peak value of the current when the driving circuit applies the driving voltage to the electromechanical transducer. 
     
     
       10. The vibratory driving device according to  claim 1  further comprising a controller which calculates the position of the movable member based on the electric resistance between the two resistive bodies measured by the measuring circuit. 
     
     
       11. The vibratory driving device according to  claim 1 , wherein the resistive body has a linear form.